A Model of Muscle Geometry for a Two Degree-Of-Freedom Planar
Arm

A muscle's action on a joint not only depends upon the muscle's size
and activation level, but also upon the mechanical advantage (or
moment arm) of the muscle upon the joint. This relationship is made
more complex by the fact that the mechanical advantage can change
drastically with skeletal configuration. Here, we describe a model of
muscle geometry for several muscles involved in elbow and shoulder
actuation. The model captures the gross changes in muscle moment arm
while preserving reasonable computational efficiency which facilitates
its use in simulation.